Our own private
experience of the world is seamless, a smooth and continous flow of sensory
impressions and perceptions of objects and events, sights and sounds.
When we see an object, such as a red ball, we do not experience the shape
of the ball separately from its color. And when we hear a violin, we do
not perceive its pitch separately from its timbre. The notes in a chord
are not heard as several individuals but rather in a more wholistic fashion.
Yes, it is possible to learn to pay more attention to one feature of a
composition at the expense of attention to other features. But this process
does not fractionate the sound into its all of its separate constituents,
the building blocks of music such as pitch, contour, interval, harmony,
melody, timbre (tone color), and rhythm.
Because our experience is so immediate, clear and effortless, we tend
to take it for granted. However, the integrated nature of our musical
and other experiences constitutes a major puzzle for brain scientists
who search for the answer to how our brains apparently effortlessly meld
all of these aspects of sound into a meaningful whole, that presents to
us personally ... music. An unlikely answer is that our brains are specialized
for music so that each of music's building blocks is processed by a different
part of the brain. The simultaneous activation of these many special purpose
processors would constitute the wholistic experience. In other words,
there is no little neural person in our brains who is listening to the
music and then telling us what it is. Although this type of idea has often
been popular, it leaves us with having to explain how the little brain
genie achieves wholistic perception of music, and so explains nothing.
amount of research findings support the first theory, that the brain is
specialized for the building blocks of music. In the first issue of Musica
Research Notes, we reviewed the evidence that the highest level of the
auditory system, the auditory cortex, processes pitch rather than raw
sound frequencies (see "A Note on Pitch", volume 1, number 1, Spring,
1994). Additionally, there are individual brain cells that process melodic
contour, the pattern of increasing and decreasing notes in music. Cells
have been found in the auditory cortex that seem likely to process specific
harmonic relationships, such as the simultaneous presentation of the second
and third harmonics of a note. Temporal, including rhythmic, aspects of
sound streams also seem to be handled by certain cells in particular parts
of the auditory cortex.
Findings from humans who have suffered damage to the auditory cortex by
stroke or by surgery to correct intractible epilepsy are particularly
fascinating. For example, damage to the right hemisphere selectively impairs
the ability to process timbre. Also, the processing of melody and rhythm
can be separated by specific brain lesions. Some patients show impaired
discrimination of melodies while they have normal discrimination of rhythms,
and vice versa for lesions in different regions. And even different aspects
of the processing of temporal information seem to be handled by different
parts of the auditory cortex, rhythm by the left hemisphere and beat (meter)
by the right hemispheres.
These dissociations of the elements of music in neurologically impaired
persons provide strong support for "building block" theory but might be
questioned by some on the grounds that the findings do not come from normal
people. This is not a very strong criticism because such patients can
show completely normal levels of performance on the capabilities that
remain. In any event, there are findings from intact people that support
and complement these neuropsychological findings. It is possible to determine
which areas of the brain are active during various tasks, including listening
to music. One powerful method is to measure increases in the regional
distribution of blood flow to parts of the cerebral cortex because these
reflect the increased metabolic needs of brain cells that are active.
In a recent study, normal subjects were tested in two passive listening
conditions, noise bursts or music matched for sound frequencies, and two
active judgement conditions, comparing the pitch of the first two notes
of melodies or the first and last notes of melodies. Listening to melodies
produced an activation of the right temporal (auditory) hemisphere relative
to the left ("language") hemisphere. Comparing notes, which also involved
short term memory, also showed a preferential activation of the right
auditory cortical system, plus some other areas of the right hemisphere.
These findings indicate that there are specialized neural substrates in
the auditory cortex of the right hemisphere that process melodies vs.
other non-melodic sounds.
preclude a more comprehensive review. However, these examples should suffice
to highlight the many types of evidence, from animals, the neurologically
impaired and the normal human, that the brain contains an organization
that is specialized to process the individual elements of music, the building
blocks of music. These findings have relevance to basic neurobiological
problems, to clinical and therapeutic approaches to treatment and last,
but not at all least, to the realization that music has a deep biological